(1) Field of the Invention
The present invention relates to a dispersing and grinding apparatus in which a grinding medium is introduced within a grinding vessel, and a material is ground and dispersed in liquid by interaction with the medium, and more particularly to a dispersing and grinding apparatus which has a rotor within the vessel to induce and circulate the medium into the passage or space provided between an outer surface of the rotor and an inner wall of the vessel for grinding and dispersing the material.
(2) Background Information
It is known that a grinding medium in a dispersing and grinding apparatus is introduced into a grinding vessel and a material is ground and dispersed in liquid by interaction of a grinding medium with an agitator. As for the agitator, agitator disks and stirring rods are often used. According to this type of agitator, it is known that a material is effectively ground as it approaches the rotating agitator due to the action of high shearing stress on the grinding material; as the material is centrifuged away or separated from the agitator, shearing stress acting on the material becomes weak, and accordingly the effective grinding of the material is difficult. As a result the distribution of shearing stress acting on the material within the vessel is not uniform. Miniaturizing the vessel might make distribution of shearing stress uniform, however, as the distance to induce the material from the inflow conduit to the outflow conduit of the vessel becomes closer, the resulting shearing stress does not act effectively on the material, and therefore satisfactory results are not obtained.
A device is also known using a hollow cylinder as an agitator. But in this king of device, flow of the medium is irregular and accordingly this type is also unsatisfactory.